To implement a total area coverage or a wide area coverage system, it is known in the art to provide a plurality of receiver sites to receive and relay the same information signal to a central receiving location. Generally, one or more of the plurality of received signals will have superior signal quality when compared to the other signals. In the mobile or portable communication environment, the signal having the highest signal quality may rapidly change as the mobile transceiver's proximity to a particular receiver site varies. Accordingly, it is necessary to continually determine which of the incoming plurality of received signals has superior signal quality, and select that signal to be received at the central receiving location.
In an analog modulation communication system, it is known to select a signal upon the basis of signal strength or received signal power. This simple criteria is generally sufficient in an analog system since the relative phases of the received signals are less critical to the selection criterion than in a digital modulation system. Accordingly, some digital selection systems have simply reconverted the digital signal into an analog signal, and compared the signals on the basis of received power as in the prior analog modulation communication systems.
Some digital selection systems have combined the plurality of received signals into a majority signal on the theory that if a majority of the received signals "thinks" the received bit should be a logical "1" the resultant majority signal bit-error-rate (BER) will necessarily be superior to any of the individual signals. Of course, the majority signal may not always have a superior BER since the mobile or portable transceiver could be in close proximity to a particular remote receiver site, thus providing one very high quality signal within the plurality of received signals. Moreover, majority selection systems suffer a severe detriment in that they, by definition, cannot operate with less than three incoming signals since there can be no majority with only two signals. Accordingly, the need exists to have a simple, inexpensive but reliable signal selection method that may operate on any number of incoming signals and overcomes the detriments of the prior art.